Multimodal dynamic robotic systems

ABSTRACT

Robotic systems according to the invention include a frame or body with two or more wheels rotatably mounted on the frame or body and a motor for independently driving each wheel. A system controller generates a signal for actuating each motor based on information provided by one or more sensors in communication with the system controller for generating feedback signals for providing reactive actuation of the motors for generating one or more functions selected from the group consisting of forward motion, backward motion, climbing, hopping, balancing, throwing and catching. A power source is included for providing power to operate the drive motors, system controller and the one or more sensors.

RELATED APPLICATIONS

This application claims the priority of U.S. Provisional ApplicationsNo. 61/231,672, filed Aug. 6, 2009, and No. 61/324,258, filed Apr. 14,2010, which are incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to robotic mechanisms that exhibitmultimodal capability including rolling, hopping, balancing, climbing,and picking up and throwing objects. More particularly, the inventionrelates to multimodal dynamic robotic systems that can move and functionefficiently on complex terrain and/or in harsh operating environments.

BACKGROUND OF THE INVENTION

Robots have been developed for applications ranging from materialtransportation in factory environments to space exploration. One area inwhich mobile robots have been widely adopted is in the automobileindustry, where robots transport components from manufacturing workstations to the assembly lines. These automated guided vehicles (AGVs)follow a track on the ground and have the ability to avoid collisionswith obstacles in their path. Autonomous mobile robots designed forplanetary exploration and sample collection during space missions, suchas NASA's Mars Exploration Rover, have also received significantattention in recent years. This attention has resulted in advancement ofmobile robot technology and a corresponding increase in theeffectiveness of mobile robots in a wide range of applications.

Mobile robot technology has primarily focused on robot designs having abody with wheels for mobility. This has led to advancements in motionplanning and control of the rolling wheel. Notwithstanding thesedevelopments, wheeled mobile robots have significant deficiencies thathave not been adequately overcome. For example, wheeled robotsfrequently have difficulty traversing rough terrain. While this problemmay be reduced by increasing the size of the wheels of the robot,increases in wheel size cause various undesirable consequences includingan increase in the overall size and weight of the robot. Further,increases in wheel sizes do not necessarily result in correspondingincreases in operational features such as payload capacity. Also,wheeled robots can be adversely affected by harsh operating environmentssuch as heat, chemicals, and the like.

A variation of a wheeled robot that addresses certain difficulties foundin harsh environments is described in U.S. Patent Publication No.2008/0230285 A1, which shares partial inventorship with the presentapplication. The cited application, which is incorporated herein byreference, describes the first vehicle of its kind which combinesefficient wheeled locomotion with a hopping capability. The multimodalrobot adds hopping and climbing capability to a wheeled robot byattaching the axle to a central leg so that relative movement of the legand axle can lift axle. A hopping action can be produced by applyingsudden downward force to drive the leg against the support surface.Stair climbing is provided by applying a steady force against thesupport surface to allow the wheels to climb up the vertical riser. Theleg also provides additional stabilization for movement across uneventerrain. In one embodiment, the multimodal robot's wheels are mounted onindependently-moving axes that have independent parallelogram linkagesto permit the wheels to change relative orientations and tilt.

One alternative to the wheeled robot is the rolling robot. A rollingrobot is one that rolls on its entire outer surface rather than onexternal wheels or treads. They tend to be spherical or cylindrical inform and have a single axle, if any axle at all, and an outer surfacethat is fully involved in the robot's movement. State-of-the-art rollingrobots are all based on the principle of moving the center of gravity ofa wheel or sphere, which causes the wheel or sphere to fall in thedirection of movement and thus roll along. Rolling robots have a numberof advantages over wheeled robots including that the components of therobot are enclosed within a shell, so there are no extremities tohang-up on obstacles, they don't fall over, they can travel on softsurfaces, including water, and they can move in any direction and turnin place.

Improvements in methods of locomotion are needed to allow roboticsystems to move within environments that are difficult or impossible forcurrently-used robot locomotion designs to traverse. The followingdescription discloses such improvements.

BRIEF SUMMARY OF THE INVENTION

It is an advantage of the present invention to provide a multimodalrobot that can move and function efficiently on complex terrain and/orin harsh operating environments.

In an exemplary embodiment, the robotic systems according to theinvention include a frame or body with two or more wheels rotatablymounted on the frame or body and a motor for independently driving eachwheel. A system controller generates a signal for actuating each motorbased on information provided by one or more sensors in communicationwith the system controller for generating feedback signals for providingreactive actuation of the motors for generating one or more functionsselected from the group consisting of forward motion, backward motion,climbing, hopping, balancing, and throwing. A power source is includedfor providing power to operate the drive motors, system controller andthe one or more sensors.

In one aspect of the invention, a robotic system according includes aframe with two or more wheels rotatably mounted thereon and a motor forindependently driving each wheel. A system controller generates a signalfor actuating each motor based on information provided by one or moresensors in communication with the system controller for generatingfeedback signals for providing reactive actuation of the motors forgenerating one or more functions selected from the group consisting offorward motion, backward motion, climbing, hopping, balancing, andthrowing. A power source is included for providing power to operate thedrive motors, system controller and the one or more sensors. The frameincludes two arms, each having a distal end on which a wheel is mountedand a proximal end and a leg centrally disposed between the two armswith the proximal end of each arm rotatably attached to the leg. An armmotor is disposed on each arm for independently driving rotation of thearm relative to the leg, so that when the leg is disposed in a verticalorientation with an end of the leg in contact with a support surface,(i) downward symmetrical rotation of the arms positions the wheels incontact with the support surface for wheeled locomotion on the supportsurface, (ii) rapid upward symmetrical rotation of the arms lifts theleg off of the support surface to produce a hopping motion; and (iii)antisymmetrical rotation of the arms balances the frame on the end ofthe leg.

In another aspect of the invention, a robotic system according includesa body with two or more wheels rotatably mounted thereon and a motor forindependently driving each wheel. A system controller generates a signalfor actuating each motor based on information provided by one or moresensors in communication with the system controller for generatingfeedback signals for providing reactive actuation of the motors forgenerating one or more functions selected from the group consisting offorward motion, backward motion, climbing, hopping, balancing, andthrowing. A power source is included for providing power to operate thedrive motors, system controller and the one or more sensors. The bodycomprises a chassis having two drive wheels rotatably mounted onopposite sides thereof, each drive wheel disposed on an axle that isrotated by a corresponding drive motor for rotating the drive wheel. Apair of elongated arms is rotatably mounted on opposite sides of andperpendicular to the chassis, each arm having a proximal end disposed ona corresponding axle, and a distal end, on which a second wheel ismounted in a common plane with the corresponding drive wheel. A secondmotor is associated with each arm, and a linkage between the secondmotor and the axle for each arm causes the second motor, when activated,to rotate one of the chassis and the corresponding arm relative to theother. Independent activation of the second motor of both arms to rotatethe arms symmetrically relative to the chassis shifts a center ofgravity for balancing on one of the distal end or proximal end of thearms. The linkage between the second motor and the axle for each arm anda linkage between the drive motor and the drive wheel can beincorporated into a two-degree of freedom joint. In one embodiment, eacharm supports a track.

In still another aspect of the invention, a robotic system accordingincludes a body with two or more wheels rotatably mounted thereon and amotor for independently driving each wheel. A system controllergenerates a signal for actuating each motor based on informationprovided by one or more sensors in communication with the systemcontroller for generating feedback signals for providing reactiveactuation of the motors for generating one or more functions selectedfrom the group consisting of forward motion, backward motion, climbing,hopping, balancing, and throwing. A power source is included forproviding power to operate the drive motors, system controller and theone or more sensors. The body comprises a chassis having two drivewheels rotatably mounted on opposite sides thereof, attached to acorresponding drive motor for rotating the drive wheel. A pair ofelongated drive arms is rotatably mounted on opposite sides of andperpendicular to the chassis, with each drive arm having a proximal enddisposed on a corresponding axle, and a distal end which supports asecond wheel in a common plane with the corresponding drive wheel. Aboom arm comprising a weighted portion attached to connector arms thatare pivotably mounted on each side of the chassis so that the weightedportion is disposed parallel to the chassis. At least one second motoris connected to the connector arms by a linkage such that activation ofthe at least one second motor rotates one of the chassis and the boomarm relative to the other. Independent activation of the at least onesecond motor shifts a center of gravity for balancing on one of thedistal end or proximal end of the drive arms. The system controllercontrols the drive motors and the at least one second motor toreactively shift the center of gravity for stability. In one embodiment,each arm supports a track.

In another aspect of the invention, a robotic system according includesa frame with two or more wheels rotatably mounted thereon and a motorfor independently driving each wheel. A system controller generates asignal for actuating each motor based on information provided by one ormore sensors in communication with the system controller for generatingfeedback signals for providing reactive actuation of the motors forgenerating one or more functions selected from the group consisting offorward motion, backward motion, climbing, hopping, balancing, andthrowing. A power source is included for providing power to operate thedrive motors, system controller and the one or more sensors. The two ormore wheels comprise a plurality of reaction wheels and the motor fordriving each reaction wheel is disposed within a housing to define aplurality of momentum exchange elements mounted on one or more axesattached to the frame. The frame comprises a geometrical structure whichallows the plurality of momentum exchange elements to be distributedabout the frame to individually or simultaneously generate angularmomentum in a plurality of different directions. In one variation, theone or more axes comprise a single gimbal axis, each having acorresponding gimbal motor. In another variation, the one or more axescomprise a double gimbal axis, each having two corresponding gimbalmotors. A shell may be provided to enclose the frame and momentumexchange elements.

In yet another aspect of the invention, a robotic system includes a bodywith two or more wheels rotatably mounted thereon and a motor forindependently driving each wheel. A system controller generates a signalfor actuating each motor based on information provided by one or moresensors in communication with the system controller for generatingfeedback signals for providing reactive actuation of the motors forgenerating one or more functions selected from the group consisting offorward motion, backward motion, climbing, hopping, balancing, andthrowing. A power source is included for providing power to operate thedrive motors, system controller and the one or more sensors. The body isconfigured as a cylinder having a rotational axis, the cylinder havingtwo ends, each end defining a hub having an axle aligned with therotational axis for rotatably retaining a wheel, the body having acavity therein defining a storage volume for retaining an object havingan object diameter. An elongated arm extends away from the bodyperpendicular to the rotational axis so that a base portion of theelongated arm is in communication with the storage volume. A lower bodyportion opposite the elongated arm is symmetrical along a planebisecting the cylinder. A curved channel is located on each side of thebisecting plane with an exit end in communication with the storagevolume and an entrance end defined by the hub, the lower body portionand an inner surface of the wheel. Each channel has a dimension forreceiving the object to produce a frictional contact between the innersurface of the wheel, the hub and the lower body portion, so thatrotation of the wheel draws the object into the channel and into thestorage volume. The drive motors are adapted for rotating the bodyrelative to the wheels so that the elongated arm can be oriented in ahorizontal position. With the elongated arm oriented in a horizontalposition, rapid activation of the motors rotates the correspondingwheels in a first direction causing the body to rotate around therotational axis in an opposite direction to rapidly accelerate thehorizontal arm toward a vertical position. An object disposed on thebase portion of the elongated arm rolls toward a distal end of the armas the elongated arm accelerates toward the vertical position, causingthe object to be thrown when the object reaches the distal end of thearm.

In a first exemplary embodiment, enhanced mobility within a harshenvironment, which may include rough terrain or hazards, is provided ina modification of a wheeled robot which combines a hopping ability witha leaning maneuver. The inventive robot includes end-over-end stairclimbing capability, which involves raising its center of mass above theobstacle while balancing the vehicle on its toe and shifting the mass ofthe drive wheels side-to side for balance.

The robot of the first embodiment comprises two independently drivenwheels mounted on the ends of two independently driven arm assemblieswhich pivot about a central leg to produce both symmetric andanti-symmetric rotation, depending on the motion desired. The armassemblies are adapted to linearly travel along the length of the legvia a non-backdriveable motorized lead screw. This gradual linear motionallows the vehicle to transition between an upright roving configurationand a toe-balancing configuration.

The independently-actuated arms can function both as a hopping mechanismwhen rotated symmetrically about the central leg, and as anactively-controlled roll-axis stabilizer when rotated anti-symmetricallyrelative to the central leg. Appropriate superposition of these twomotions allows the robot to simultaneously stabilize and hop in the rollaxis plane.

The multimodal robot of the present invention improves upon previousdesigns by leveraging a highly-efficient leaning maneuver whileretaining the hopping capabilities necessary to overcome otherobstacles, including jumping onto a raised platform or across a gap, orquickly traversing flames or other hazards that could damage aslower-moving robot.

Applications for the multimodal robot of the first embodiment includereconnaissance in burning or chemical-contaminated environments,monitoring hazardous materials (e.g. nuclear waste stockpiles),providing mobile platforms for weapons, planetary exploration, and forincorporation in toys.

A second embodiment of a multimodal robot combines rolling, balancingand climbing capabilities in a wheeled or treaded vehicle by changingthe vehicle's center of gravity relative to its chassis. These multiplemodes of operation allow the vehicle to perform and stabilize “wheelies”and “reverse wheelies” (also known as “stoppies”). In an exemplaryembodiment, the robot is capable of overcoming obstacles nearly as tallas the vehicle is long (in its folded configuration) by reconfiguringitself to adjust its center of gravity. A platform or frame ispreferably connected to the chassis to carry a payload, sensors, camerasor other electronic devices. In a preferred configuration, motors thatdrive the treads or wheels are capable of independent rotation withrespect to the chassis, so that the treads or wheels may be used in boththe rolling and balancing functions. This allows the robot todynamically adjust its center of gravity. MEMS accelerometers andgyroscopes, coupled with advanced filtering techniques, allow the robotto estimate its angle with respect to gravity. With the tread assembliesunfolded away from the body, the robot can balance upright on itstreaded “toes” and stand up in order to expand the view of an onboardcamera (or other sensors) and overcome obstacles that would otherwise beinsurmountable with a treaded robot that is of the same height as therobot in its conventional treaded mode. This design is also capable ofboth crossing chasms nearly as wide as the vehicle is long, and usingthe front-mounted pivot of the chassis to actively dampen vibrationswhen driving quickly over rough terrain. The reconfigurability of thetread assemblies permits several modes of locomotion, which can beselected to adapt the robot to the type of terrain encountered. Theunique mechanical design of this multimodal robot coupled with feedbackcontrol algorithms enables it to overcome complex terrain (e.g. stairs,rubble) while retaining a small form factor to navigate in confinedspaces and to reduce cost and weight.

In an alternative configuration, an actuated boom is included tofacilitate balancing and climbing. The boom has significant mass,approximately equal to the mass of the chassis. Motors are configured onthe robot to drive the treads (or wheels) and to change the angle of theboom with respect to the chassis. Sensors are integrated to detect therobot's configuration, including one or more level sensors along eachaxis, which provide signals to a system controller. Feedback may beapplied to enable the vehicle to balance on its front or rear treadedtoes (or wheels). The vehicle can also climb obstacles (includingstairs) by extending the mass of the boom over the obstacle and rotatingthe chassis up and over. This maneuver may be done in a staticallystable manner or in a dynamically balanced manner. The boom arm may beextensible and/or may be configured with its own wheels or treads,

The shifting of the robot's center of gravity allows it to overcomeobstacles nearly as tall as the vehicle is long (in its foldedconfiguration) by repositioning its boom arm.

Applications of this multimodal robot include building, cave, and mineexploration; search and rescue; monitoring hazardous materials (e.g.nuclear waste stockpiles); improvised explosive device (IED) detectionand disposal; weapons platform; toy; planetary exploration; HVAC systemmonitoring.

In a third embodiment, motion in harsh operating environments and uneventerrain is provided by a spherical robot that incorporates momentumexchange devices to achieve rapid acceleration or deceleration in anydirection.

The inventive spherical robot can efficiently traverse a wide variety ofterrain including, but not limited to: carpet, pavement, sand, gravel,and mud. In addition, it can incorporate an amphibious capability whichallows it to traverse mud, swamp, and open water. Unlike existingspherical robots, the internal frame of the present embodiment is fixedto the external sphere and the center of mass of the robot remains fixedto the center of the sphere. In an exemplary embodiment, single-gimbaledcontrol moment gyroscopes (CMGs) are used for momentum exchange. Thisdesign is especially agile, as the momentum needed to maneuver is storedwithin the CMGs and, thus, does not need to be generated by high-torque(and large electrical power-consuming) motors like a standard directdrive system.

In one embodiment, a cubical frame is populated with four single-gimbalCMGs, with each gimbal axis at an angle on each face. A plurality ofother momentum exchange devices such as reaction wheels, dual-gimbalCMGs, or momentum wheels may be incorporated as alternatives to thesingle-gimbal CMGs. The robot is not limited to spheres as an outerstructure, but to all generalized amorphous ellipsoidal configurationsas well.

In military applications, the inventive spherical robot can be used incovert reconnaissance or munitions delivery. For the general commercialapplications, the robots can be a toy or a therapeutic device.

The fourth embodiment of the multimodal robot is a wirelessly-controlledor autonomous vehicle which is an all-in-one system of ball retrieval,storage and throwing. The design includes an integrated ball pick upmechanism and the jai alai style throwing arm design.

To enable ball pick up, the body and wheels of the robot are spaced toprovide automatic pickup and loading of the target balls. This methodallows the operator to drive the robot toward the target, with thecurvature of the robot directing the ball into the space between thewheel and the body. The rotation of the wheel brings the ball up to bestored within a basket or other storage receptacle.

For throwing, the robot is stabilized by a feedback control circuit tobalance upright as an inverted pendulum. The great rotational inertia ofthe wheels allows the robot to rotate the body quickly from a lay-downmode to an upright mode. The rapid rotation results in the effectivetoss of a light weight ball. The ball is imparted with a spin as itrolls off the throwing arm track. The result is a more stable and longerthrow.

The potential applications of the present robot embodiment includeremote controlled toy cars, an automatic tennis ball retrieval system,and a grenade launcher, among others.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 a is a diagrammatic front view of a first embodiment of themultimodal hopping robot; FIG. 1 b is a detail view of the circled areain FIG. 1 a.

FIG. 2 is a diagrammatic perspective view of the hopping robot of FIG.1.

FIG. 3 is a diagrammatic perspective view of the arm assemblies of thehopping robot.

FIG. 4 is a series of cartoons illustrating the modes of operation ofthe robot of FIG. 1.

FIGS. 5 a and 5 b illustrate configuration of the arm assemblies duringmotion, where FIG. 5 a shows a hopping motion; FIG. 5 b shows asymmetricarm motion for stabilization about the roll axis.

FIG. 6 is a diagrammatic front view of the multimodal hopping robot inan upright roving configuration.

FIG. 7 diagrammatically illustrates a self-locking arm suspensionmechanism.

FIG. 8 diagrammatically illustrates an alternative embodiment of the armsuspension mechanism.

FIG. 9 is a series of plots of effective spring resistance due tosymmetric rotation, showing angular displacement as a function of springstretch, resultant torque and effective torsional spring rate.

FIG. 10 is a series of plots of effective spring resistance due toantisymmetric rotation, showing angular displacement as a function ofspring stretch, resultant torque and effective torsional spring rate.

FIG. 11 is a plot of critical zero-torque arm angle (symmetric rotation)as a function of linkage parameters.

FIG. 12 is a perspective view of the arm mechanism of the hopping robotduring conventional operation.

FIG. 13 is a perspective view of the hopping robot in a horizontalroving configuration.

FIG. 14 a is a diagrammatic perspective view of a multimodal robotaccording to a second embodiment; FIG. 14 b is a diagrammatic side viewof an exemplary tread assembly.

FIGS. 15 a-15 c illustrate different modes of locomotion of theembodiment of FIG. 14, where FIG. 15 a shows the robot in aheel-balancing position, FIG. 15 b shows the robot in a toe-balancingposition, and FIG. 15 c showing the robot with its treads extended forreaching across and spanning a gap, or for climbing.

FIGS. 16 a-16 c illustrate an alternative configuration of themultimodal robot of FIG. 14, in which an actuated boom is used to shiftthe robot's center of gravity.

FIG. 17 illustrates an alternative configuration of the multimodal robotof FIG. 14 in which the treads are replaced with wheels.

FIG. 18 illustrates an alternative configuration of the multimodal robotof FIG. 16 a.

FIG. 19 is a diagrammatic view of the components of a hip joint of thesecond multimodal robot embodiment.

FIGS. 20 a-20 e are perspective views of the treaded robot, where FIG.20 a shows the robot in a horizontal skid steer configuration; FIG. 20 bshows the robot in a “chasm-crossing” configuration; FIG. 20 c shows therobot in a vertical “C-balancing” configuration; and FIG. 20 d shows therobot in a vertical “V-balancing” configuration.

FIGS. 21 a and 21 b illustrate examples of functions performed by themultimodal robot of FIG. 14, where FIG. 21 a is a perspective view ofthe robot maneuvering within a duct, and FIG. 21 b is a perspective viewof the robot perching on the edge of a stair step.

FIG. 22 illustrates a sequence of steps in a climbing operationperformed by the robot of FIG. 14.

FIG. 23 is a diagrammatic perspective view of a spherical robotaccording to the third multimodal robot embodiment.

FIGS. 24 a-24 c are diagrammatic views of three different prior artmomentum exchange devices that may be used in the spherical robot, whereFIG. 24 a illustrates a reaction wheel assembly; FIG. 24 b shows asingle gimbal control moment gyro; and FIG. 24 c illustrates a doublegimbal control moment gyro.

FIG. 25 is shows four exemplary geometric configurations for a frame forsupporting the momentum exchange elements.

FIG. 26 is a three-dimensional computer drawing of a first exemplaryconstruction of the spherical robot.

FIG. 27 a is a perspective drawing of a second exemplary construction ofthe spherical robot; FIG. 27 b is an exploded view of the construction;FIG. 27 c is an exploded view of one SGCMG element.

FIG. 28 is a block diagram showing the sequence of control operationsfor the spherical robot.

FIGS. 29 a-29 c illustrate examples of possible functions that can beperformed using the spherical robot, where FIGS. 29 a and 29 b showexamples of motion of the robot in a free-surface case and anear-a-surface case, respectively; and FIG. 29 c is a series of cartoonsshowing the steps of a process for coordinating multiple sphericalrobots to overcome an obstacle.

FIG. 30 is a perspective view of a fourth multimodal robot embodiment.

FIGS. 31 a and 31 b are a front view and a rear view, respectively, ofthe body portion of the multimodal robot of FIG. 30.

FIGS. 32 a and 32 b are side views of the body portion with the wheelremoved showing steps in a sequence for picking up a round object.

FIG. 33 is a perspective view of latch for preventing the object fromrolling backward in the channel.

FIGS. 34 a and 34 b are side and perspective views, respectively, of aball release mechanism.

FIGS. 35 a-35 c are cross-sectional views of the robot body showing theball release sequence.

FIGS. 36 a-36 d are side views of the robot showing the throwingsequence, where FIG. 36 a shows the ball at the lower portion of thethrowing arm; FIG. 36 b shows the beginning of the body rotation to movethe ball to a mid-point of the throwing arm; FIG. 36 c shows the ball atthe upper portion of the throwing arm; and FIG. 36 d shows the ballafter release.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The following description of four embodiments of multimodal robotsprovide details of functions including locomotion via rotation of wheelsor tracks and spherical rotation, hopping, climbing, and throwing. Whilethe different embodiments may use different locomotion means, the commonfeature among all embodiments is their use of feedback to controlangular momentum to enable active balancing and effect changes inorientation and movement of the robots, resulting in vehicles that canbe used in a wide range of applications from military and industrialapplications to toys.

First Multimodal Robot Embodiment

Referring initially to FIGS. 1-3 and 6, the robot 10 of the firstembodiment (which may also be referred to herein as a “vehicle”)includes two independently driven wheels 6, 8 mounted on the ends of twoindependently driven arm assemblies 12, 14 which pivot about centralleg/shaft 16. The arm assemblies 12, 14 travel linearly along the lengthof leg 16 by way of a non-backdriveable motorized leadscrew 20. Thegradual motion provided by the screw 20 allows the vehicle 10 totransition between an upright roving configuration and a toe-balancingconfiguration. FIG. 2 illustrates the three rotational axes around whichthe inventive robot moves, with leg 16 corresponding to the yaw-axis,the axles of the drive wheels corresponding to the pitch-axis, and thearm carrier 21, to the extent that it defines the midpoint in the armassembly, corresponding to the roll-axis.

Referring to FIG. 2, arm assemblies 12, 14 are linked to a central armcarrier 21 via joints 11 and 13, which extend through leg guide channels48 and 49. The arm carrier 21 is driven linearly along the leg 16 via aleadscrew powered by motors within the arm carrier to move joints 11 and13 along the lengths of the guide channels.

Left arm assembly 12 includes a parallelogram linkage, which has thebasic “frame” elements of a top left arm 22, bottom left arm 23, leftarm end link 30 and left arm mid-link 25. Similarly, right arm assembly14 includes the frame element of top right arm 18, bottom right arm 19,right arm mid-link 50 and right arm end link 47. The frame elements ofthe arms are preferably formed from a lightweight but relatively rigidmetal, such as aluminum or titanium. Alternatively, the frame elementsmay be formed from a strong, rigid plastic or other polymer. The jointsand drive mechanisms that connect and allow manipulation of the framebasic elements are described in more detail below.

The top left arm 22 attaches to the arm carrier 21 via joint 11, whichattaches to the left arm end-link 30 via joint 31. The bottom left arm23 is attached to left arm end-link 30 via joint 32 and to the armcarrier 21 via joint 13. The left arm mid-link 24 attaches to the topleft arm 22 via joint 4, and to the bottom left arm via joint 3. In allcases, the joints described herein are revolute joints.

The left spring lever 25 is attached to the left arm assembly via joints33 and 34. As illustrated, joint 34 is horizontally offset from themidpoint of a line connecting joints 31 and 32. The attachment betweenthe spring lever 25 and joint 34 consists of a standard revolute jointcoaxial with joint 34. Joint 34 attaches to either a linear bearing(free to travel along the line connecting the endpoints of the springlever 25) affixed to the spring lever, or to a straight-line “Watts”linkage 70, details of which are shown in FIG. 1 b, consisting of thelinks 60, 61 and 62 and connecting joints 36, 37, 38 and 59. The armassembly 12 will not move if the spring lever 25 attaches directly tojoint 34 without some form of linear bearing/prismatic joint orstraight-line linkage. Left spring lever 53 is attached to the right armassembly via joints 55 and 56 in conjunction with a similar Wattslinkage.

The left arm assembly 12 is actuated via torque applied to left chaindrive sprocket 41 at joint 32. Sprocket 41 engages the output shaft 29of the arm motor 27, which is centrally mounted within the left armend-link 30. The right arm assembly 14 is similarly actuated, with rightchain drive sprocket 39 engaging the output shaft (not shown) of rightarm motor 51, which is mounted within right arm end link 47.

Two extension springs 5, 52 connect the two arm assemblies. Left spring52 connects the proximal end of the left arm spring lever 25 at joint 35to the right spring pre-tension pulley 54 (visible in FIG. 3) of theright assembly. Similarly, right spring 5 extends between the proximalend of the right arm spring lever 53 and the left spring pre-tensionpulley 26. Spring tension may be adjusted by rotating the springpretension pulleys 26, 54 in the appropriate direction. Such adjustmentcan be accomplished by applying torque via the arm motors 28, 51 whiletheir respective arm motor clutches 28, 44 are disengaged. Since the armmotor output shaft 29 (right shaft not shown) has a finite range oftravel, this will eventually result in rotation of the arm motor body28, 51, which engages the respective spring pre-tension pulley 26, 54via a single-stage spur gear transmission.

FIG. 4 illustrates possible modes of operation of the inventive robot.Using the combination of the independently-driven wheels 6, 8, theleadscrew 20 and the independently actuated arms 12, 14, the robot canuse one or a combination of motions to perform useful functions duringoperation of the vehicle. Horizontal roving (a) is effected when theleft and right drive wheels are rotated in the same direction to tiltthe leg forward. The wheels continue driving in the same direction tomove the vehicle forward with the end of the leg on the support surface.To steer, the wheels may be operated in opposition to each other. Theindependent operation of the wheels allows the robot to be turnedquickly on a point, or with a very small turning radius. As can be seenin the perspective view of FIG. 13, horizontal roving mode gives thevehicle a low vertical profile, allowing it to pass easily beneath lowobstacles, such as fences, wires, or low shrubs, and to avoid opticalsensors that may be positioned several inches or more above the floor orsupport surface.

An uprighting maneuver (b) from the horizontal roving mode involvesapplying a sudden strong torque to the wheels in the appropriatedirection. When reaction wheels are torqued in one direction, thevehicle experiences an equal-and-opposite reaction torque. Asillustrated, a strong clockwise torque induces a counter-clockwiserotation of the leg to rotate the leg into a vertical position. Themotion of the reaction wheel itself can later be bled back off, eitherwith reaction control thrusters, or merely when the vehicle comes backin contact with the support surface. The instantaneous torque availablewhen using reaction wheels is limited to that provided by the motor usedto drive the reaction wheels themselves. In the upright mode, the robotdrives only on the reaction wheel wheels, with the leg pointed upward toproviding a raised support frame for mounting vision systems or othersensors to expand the sensor's range for surveying the surroundings.

For upright balancing and roving (c) in the fore-aft direction,toe-balancing (e) and hopping (d), reaction-wheel stabilization may beused. The reaction wheels can be used as counterweights in theleft-right direction (akin to a tight-rope walker's balance bar).Finally, the reaction wheels may act as counterweights for the stiffelastomer spring to work against in order to achieve the actual hoppingmotion of the vehicle in either conventional monopedal locomotion (f) orcartwheeling monopedal locomotion (g).

The mass of the wheels should be significant in order for the last threeof these functions (e, f and g) to be viable. In the exemplaryembodiment, the mass of each of the wheels is provided by the vehiclebatteries 7, which are distributed symmetrically around the outer hub ofeach wheel, and the motors 45 (within their corresponding motor housings9) that are used to drive the wheels 6, 8. By exploiting the weights ofthese relatively heavy components as opposed to adding dead weight tothe wheels, the overall mass of the robot can be minimized.

The independently-actuated arms 12, 14 can function both as a hoppingmechanism when rotated symmetrically about the central leg 16 (aroundthe roll-axis) and as an actively-controlled roll-axis stabilizer whenrotated anti-symmetrically about the central leg. A hopping motion,shown in FIG. 5 a, is created by, starting from a configuration with thearms angled downward (indicated by grey lines in FIG. 5 a), rapidlyrotating the arms 12, 14 symmetrically upward relative to the leg 16,abruptly stopping as they reach a horizontal orientation. One or morelevel sensors (not shown), which may be located on the arm assemblies12, 14 and/or on the leg 16, may be used to generate electrical signalsthat are communicated to the vehicle's controller (not shown). In anexemplary embodiment, the controller may be incorporated in one or morecustom and/or commercial off the shelf (COTS) printed circuit boards(PCBs), such as the C200 MCU available from Texas Instruments. The PCBswill preferably be enclosed within a protective housing that can beattached to the leg 16 in a way that does not interfere with operationof the leadscrew. Feedback from the level sensors may be used to controlthe anti-symmetric arm motion for balancing. As illustrated by FIG. 5 b,anti-symmetric arm motion generates an equal and opposite torque aboutthe leg 16, enabling feedback stabilization about the roll-axis.Appropriate superposition of these two motions allows the robot tosimultaneously stabilize and hop in the roll-axis plane. The majority ofthe vehicle's mass should be concentrated at the ends of the arms inorder for the arms to effectively hop and balance the vehicle.

In the preferred embodiment, the leg 16 should be formed from a materialthat is light while maintaining sufficient stiffness to avoid bucklingor introducing excessive structural flexibility. Lightweight steel,aluminum and titanium are examples of appropriate materials.

When out of ground contact, the wheels 6, 8 provide pitch-axis stabilityby actively applying torque, using the same principle as theanti-symmetric action of the arms. The arm assemblies 12, 14 areconfigured in a parallelogram linkage so as to maintain constant angularalignment of the wheels 6, 8 relative to the central leg 16 throughoutthe arm's range of motion. This simplifies the overall dynamics bypreventing strong coupling between the pitch- and roll-axis dynamics. Inthis configuration, the top and bottom arms 18, 22 and 19, 23,respectively, preferably have an outward curvature at their lengthwisecenters, as shown, in order to prevent interference between coplanarcomponents. In other words, the ends of the arm sections curve inwardrelative to their midpoints. A simpler configuration in which the wheelsare directly attached to a single link would function similarly forsmall angular deflections (+/−15 degrees) of the arms.

In the preferred embodiment, the left and right arm motors 28, 51 arehigh-speed/low-torque in order to optimize hopping performance. The armsare spring-loaded by extension springs 5, 52 to support the weight ofthe arms and to recover energy during hopping. While this springmechanism should strongly resist motion of one arm relative to the otherin order to support the weight of the wheels during hopping, it shouldnot substantially resist rotation of either arm relative to the centralleg 16. This arrangement allows the anti-symmetric rotation necessaryfor active roll-axis stabilization.

While placing a torsion spring across the arms fulfills these basicrequirements, additional functionality can be realized via a moreintricate linkage mechanism. Specifically, since each arm is actuated bytorque applied at one of the outward joints by the correspondinghigh-speed/low-torque motor 28, 51, a digressive stiffness (decreasingwith increasing deflection) is desirable in order to provide a moreconstant resistance to symmetric motion; i.e., provide high support atsmall deflections, without overwhelming the motors at large deflections.Secondly, in order to facilitate multimodal operation, the effectivespring rate is preferably adjustable on-the-fly, without introducingtorsional bias/asymmetry. Lastly, in order to store energy for largejumps (and to keep the vehicle in a folded configuration during roving),the arms should preferably self-lock into a fully-tensioned statewithout requiring additional actuators. Furthermore, the angulardeflection at which locking occurs must be less than 90 degrees in orderto prevent collision between coplanar mechanism links.

In the preferred embodiment, the self-locking feature is achieved byincorporating a pair of non-coplanar springs 5, 52 attached to springlevers 25, 53 within the parallelogram linkage. The relationship betweenthe springs 5, 52 and levers 25, 53 is illustrated in FIG. 7, whichshows how the top plane and bottom plane function separately andcombined (right). The top plane, shown on the left in FIG. 7, includesright spring 5, left spring lever 25, and joint 34′, which includesjoint 34 and Watts linkage 70. The bottom plane, shown in the center ofthe figure, includes left spring 52, right spring lever 53, and thejoint corresponding to left joint 34′, which includes joint 55 and itsassociated Watts linkage (or other appropriate linkage.) The black dotsin the line drawing correspond to the respective joints identified inFIGS. 1-3. FIG. 8 illustrates the kinematic equivalent realizations ofthe arm suspension mechanism shown in FIG. 7.

As illustrated by the curves plotted in FIG. 9, the resistance tosymmetric motion decreases with increasing deflection from horizontal,(arms outstretched, as in FIG. 1), measured as angular displacement(α_(L)=−α_(R) [deg]), and eventually changes sign past a certaincritical angle (“0” in the plots). This causes the arms to lock into afully tensioned state, provided that the arms are constrained to deflectat most slightly past this critical zero-torque angle. In FIG. 9,angular displacement is plotted relative to percentage spring stretch,resultant torque (in Newton meter), and effective torsional spring rate(in Newton meter/radian), respectively, at four different levels ofspring pre-tension. FIG. 10 illustrates the resistance to anti-symmetricrotation under varying levels of spring pre-tension using the samecomparisons used in FIG. 9. FIG. 11 is a plot of the criticalzero-torque arm (locking) angle as a function of varying link lengthsfor symmetric rotation, where B/L=0.125, C/L=1.094, and D/L=0.438.

Note that the symmetric configuration enables bi-directionalseries-elastic actuation using the extension spring. Referring to FIG.12, during conventional operation, the main body of left arm motor 28 isheld stationary by a small actuated clamp 62. Loosening clamp 62 allowsthe motor 28 body to rotate. This, in turn, drives left springpre-tension pulley 27 around which the one end of extension spring 25 iswound. Similarly, right arm motor 51 may be rotated by loosening itscorresponding clamp (not visible in the figures) to drive rightpre-tension pulley 54 to adjust the tension on spring 5. These featuresallow the springs to be pre-tensioned while the arms 12, 14 are lockedat the maximum extent of travel by loosening the clamps 62, and drivingthe motors 28, 51 in the direction that causes downward arm motion (inorder to prevent unlocking). Note that, since the springs 5, 25 arealways in tension, they may be tightened by driving the correspondingpulley 27, 54 in either direction. Additionally, the motors 28, 51 mayactuate in series with the springs 5, 25 by loosening the clamps. Thisis sometimes referred to a “series elastic actuation” and may be usefulfor buffering mechanical energy, and isolating the motors 28, 51 frommechanical shock.

As described above, each drive wheel 6, 8 has two wheel motors thatpropel and steer (via differential drive) the vehicle when in contactwith the support surface. Referring to FIGS. 1 and 2, on right drivewheel 8, two wheel motors 45 are fixed on the wheel hub via housing 9.The drive gears of motors 45 engage spur gear 40, which is mounted onaxle 46. As previously mentioned, the batteries 7 are located on eachwheel hub to provide the added weight needed for balancing, hopping andmonopedal motion. On the left side, drive wheel 6 has two motors 45 thatdrive spur gear 42 to rotate the wheel around its corresponding axis.

In an alternative embodiment, the drive wheels may be replaced by asecond set of arms mounted in an orthogonal arrangement with the armassemblies 12, 14. This provides a pitch-axis arm pair and a roll-axisarm pair. In this embodiment, level sensors may be provided within boththe pitch- and roll-axes to provide the feedback needed to controlanti-symmetric arm motion within both axes. The resulting structure canprovide highly stable monopedal locomotion that can balance in multipleaxes. Since the weights of the wheels and their corresponding drivemotors are eliminated in this embodiment, additional weight may need tobe added to the end of each arm assembly to provide the mass needed forhopping and toe balancing.

The multimodal robot of the first embodiment can be fitted with optical,audio, thermal, chemical and other environmental sensors, or acombination of different sensors, which can be used to provide inputinto an adaptive system controller, e.g., artificial intelligence toallow the vehicle to develop a situational awareness that will permitpredictive path planning in complex environments. Alternatively, or inaddition, the vehicle can have incorporated into its electronics atransceiver for receiving remote commands and for transmittinginformation collected by its sensors.

The robotic system described herein is useful for maneuvering withincomplex structures or rugged terrain via different combinations ofhopping, pole climbing, toe balancing, horizontal roving and uprighting,all in a controlled fashion. For example, the robotic system can climbstairs using a combination of pole climbing and toe balancing to climbstairs.

Second Multimodal Robot Embodiment

A second multimodal robot 100, illustrated in FIGS. 14, 15 and 20, is atreaded vehicle that can perform stable both heel and toe standing,i.e., “wheelies” and “stoppies”, and can balance on the edge of a stepor similar change in elevation. As shown in FIG. 14 a, multimodal robot100 includes a pair of arms 110 and 120 which comprise independent treadassemblies that are attached to chassis 102 by way of tread shaft 108.In the exemplary embodiment, a single chassis holds the actuators,sensors, electronics, and batteries required for operation andcommunication with the robot. Rotation of the shaft 108 causes the treadlinks to advance for translational movement; rotation about the shaftcauses the entire tread assembly to rotate with respect to the chassis.This unique “hip joint” is described in more detail below. An optionalplatform 104 may be attached to chassis 102 to provide a support forattaching sensors, cameras, or other equipment or instruments to betransported on the robot. Where no platform is provided, a housing maybe provided to enclose the chassis and any associated electronics,batteries or actuators. If a platform 104 is included, the chassishousing and platform can be the same structure (as illustrated, chassis102 is separated from platform by a dashed line), or the chassis housingcan be fully or partially enclosed within the platform. It should benoted that platform 104 is not limited to a rigid structure—it may be arigid or a deformable body which may be passively or actively deformedto adapt the robot as required for a particular task. Further, theplatform need not be a solid, enclosed structure, but can be an openframe or a combination of open and closed portions.

One or more sprockets may be driven with an actuator such as a motor,engine, or pneumatic or hydraulic turbine. As illustrated in FIG. 14 b,which is a simple diagram showing the components of a tread assemblywith a side cover removed, each tread assembly includes two or moretread sprockets 114, 116 rotatably mounted in the same plane on avertical side plate or frame 111 to engage tread 112. One or more treadguides 115 may also be rotatably mounted on frame 111. Tread sprocket114 is mounted coaxially with shaft 108. One or both sprockets 114 maybe mounted with a sensor to measure position, speed, and/or torque. Aforce or pressure sensor may optionally be provided underneath a span ofthe tread 112 to detect where the tread assembly is in contact with theground or other surface. Mechanisms as are known in the art foradjusting the tension of the tread may also be included. Controlelectronics, batteries, and communications electronics may be mountedwithin the tread arm 110, or may be housed within chassis 102 orplatform 104, if appropriate.

Referring briefly to FIGS. 20 b and 20 c, wheels 124 may be rotatablymounted near the edge of platform 104, opposite the chassis, to furtherexpand the robot's functionality. For example, in FIG. 21 a, the robotis shown maneuvering within a duct 128 or other narrow passageway byeffectively wedging itself between opposite sides of the duct. Thewheels 124 allow the robot to apply pressure perpendicular to the sideof the duct as the robot moves forward along the length of the duct.Sensors within the treads or attached to the tread shaft are preferablyincluded to provide feedback to allow the robot's controller to adjustthe relative angles of the chassis and treads to maintain the pressureneeded to allow the robot to progress through the duct or passageway.The wheels 124 may be attached to freely rotate around their axles, orthey may be attached to the drive shaft of one or more additional motorsfor providing an additional degree of control.

A variation on the embodiment of FIG. 14 a is illustrated in FIG. 17,where the tread assemblies are replaced with a corresponding wheelassembly, which includes two or more wheels 117, 118 rotatably mountedin a planar relationship on the arms 119. In this embodiment, a drivechain or other linkage should be provided to drive wheels 117 and 118together in order to perform toe balancing or other maneuvers thatrequire force to be applied at the distal or toe end of the arm 119.Axle 108 extends from chassis 102 as above to drive wheels 118. Thefollowing descriptions of the robot's “hip joint” and maneuvers enabledthereby are equally applicable to the treaded version of FIG. 14 a andthe wheeled configuration of FIG. 17.

Referring to FIG. 19, in the preferred embodiment, a two degree offreedom joint is used in the mobile robot of FIG. 14 a to connect eacharm 110, 120 (or 119 in the wheeled version), to the chassis 102 andtransmits two decoupled, yet coaxial, torques. The torque to advance thetreads 112, 122 (or rotate the wheels) is transmitted by coupling thetread shaft 108 on one end to a motor 140 and on the other to the drivesprocket 114 (or wheel). This shaft passes through, and spins freelyrelative to, a tread gear 130, which is rigidly mounted to the arms 110,120 (or 119). A pinion gear 132 mounted to a second shaft 136, parallelto the tread shaft 134, causes the pinion gear 132, and arms 110, 120(or 119), to rotate with respect to the chassis 102 when driven by thesecond motor 142, which may also be referred to as the boom motor. Thisassembly provides for the adjustment of the center of gravity, as willbe discussed in more detail below. A slip ring 144 (with one or morechannels) may be located coaxially with the first shaft 108 in order totransmit and receive power and/or electrical signals between the chassis102 and arms 110, 120 (or 119) throughout a continuous range ofrotation. Optical encoders 134 may be included to measure the angle ofthe chassis with respect to arms 110, 120 (or 119) to provide feedbackto the control system. In an alternative configuration, the componentsof the hip joint, i.e., all motors, gears and sensors, may be located inthe arms, such that the chassis can simply be an axle that joins theshafts 108 of two arms 110, 120 or 119 together.

The embodiments of FIG. 14 and FIG. 17 are capable of independentlyrotating the arms 110, 120 (or 119) with respect to the chassis 102 inaddition to driving the treads 112, 122 (or wheels 118). This allows therobot to dynamically adjust its center of gravity.Commercially-available MEMS accelerometers and gyroscopes, coupled withadvanced filtering techniques, allow the robot to estimate its anglewith respect to gravity. With the arms 110, 120 unfolded away from thebody, the inventive multimodal robot can balance upright on the distal(with respect to the tread shaft 108) end of the arms, as illustrated inFIGS. 15 b and 20 c, making it possible to significantly expand therange of an on-board sensor or instrument, such as a camera. Anexemplary robot with tread assemblies on the order of 10-15 cm high and30-50 cm long may be able to stand up to 65 cm tall and overcomeobstacles that would otherwise be insurmountable with a 10-15 cm talltreaded robot. The inventive design is also capable of both crossingchasms nearly as wide as the vehicle by extending the arms in oppositedirections, as illustrated in FIGS. 15 c and 20 b. Further, thefront-mounted pivot of the chassis may be used to actively dampenvibrations when driving quickly over rough terrain. Thereconfigurability of the arms permits several modes of locomotion, whichthe inventive robot can switch between based on the type of terrainencountered. As illustrated in FIG. 15 a and FIG. 20 d, the robot canbalance on the proximal (with respect to the tread shaft 108) end of thearms, i.e., perform a wheelie, with the proximal end of the arms 110,120 in contact with the ground and neither the chassis 102 nor thedistal end of the arms in contact with the ground. This can be referredto as the “V-mode”. The angle between the chassis 102 and the arms 110,120 may be changed by actuating the boom motor where the tread motorwill be actuated as needed to keep the changing center of gravity overthe contact point to keep the robot from falling over. This change inangle may be the result of a reference command sent by an operator orperformed automatically by the robot in response to an external stimulusor as part of a programmed sequence. This maneuver can be used toinitiate a climbing sequence, for example. In FIGS. 15 b and 20 c, therobot is illustrated in a toe balance, or a “stoppie”, which isperformed by placing the distal end of the arms 110, 120 in contact withthe ground and neither the chassis 102 nor the proximal ends of the armsin contact with the ground. This can be referred to as the “C-balancingmode.” The angle between the chassis 102 and the arms 110, 120 may bechanged by actuating the boom motor where the tread motor will beactuated as needed to keep the changing center of gravity over thecontact point. This change in angle may be the result of a referencecommand sent by an operator or performed automatically by the robot inresponse to an external stimulus or as part of a programmed sequence.The multiple modes of locomotion according to the inventive mechanicaldesign coupled with feedback control algorithms will enable the robot toovercome complex terrain, such as stairs, rubble, and other obstacleswhile retaining a small form factor to navigate in confined spaces andto reduce cost and weight. In a preferred embodiment, the on-boardelectronics includes wireless communication circuitry, as is known inthe art, to enable bidirectional communication over WiFi. In anespecially preferred embodiment, the robot includes appropriateelectronics and programming to enable the robot to communicate with oneor more computers, other robots, and mobile devices, such as a cellulartelephone by using, for instance, the IEEE 802.11g standard.

Examples of complex tasks that can be performed by the treaded/wheeledrobot are illustrated in FIG. 21 a, which was discussed above, and FIG.21 b, which illustrates a portion of a stair climbing maneuver as wellas showing how the treaded robot is capable of “perching” on smallsurfaces, such as the edge of a stair (126), a branch, or a telephone orpower line. In this configuration, the treads of the robot are incontact with the surface at one point and the robot maintains itsbalance by adjusting the chassis and/or boom to keep its center ofgravity in line with the contact point. Inertial sensors (e.g.,accelerometers and gyroscopes) may be used in conjunction with contactsensors (e.g., force sensitive resistors) inside the tread assemblies todetermine the contact point. Active balancing provided by thecombination of the tread and balancing motors and continuous feedbackfrom the sensors to control the motors maintains the robot's center ofgravity to stabilize it sufficiently to hold its position. The center ofgravity is shifted in the desired direction when the robot is made toclimb up or climb down the stairs 126 so that the center of gravity iskept directly above the contact point using a combination of modes ofmovement.

FIG. 22 illustrates one example of operations that may be performed bythe above-described multimodal robot for climbing an obstacle such as astaircase. In step (1), the robot approaches the step while balancing onthe distal end of the arms (in “C-balancing” mode, as illustrated inFIGS. 15 b and 20 c). In steps (2) and (3), upon arriving at the step,the position of the chassis is adjusted such that the center of mass isdirectly above the edge of the first step. In steps (4) through (7), viaa coordinated combination of tread actuation and appropriate variationof the angle between the treads and the chassis, the robot balances onthe edge of the step while gradually edging up the step.

In one realization of this maneuver, the angle between the treads andthe chassis is actuated as a function of time based on what is required,nominally, to keep the center of mass over the edge of the step whilemaintaining the desired angle between the chassis and horizontal, whilethe contact point between the treads and the edge of the step moves(relatively slowly) along the arm; balancing is then achieved viafeedback control applied (relatively quickly) via tread actuation. In asecond realization of this maneuver, feedback control is applied via acoordinated application of both tread actuation and small adjustments tothe angle between the treads and the chassis.

Upon reaching the top of the step, there are two possible scenarios: Thefirst is that vehicle has either reached the top of the stairs, or theangle of the edges of successive steps from horizontal is less than theangle of the chassis from horizontal (that is, the angle of the steps isrelatively shallow). In either situation, the vehicle simply returns toC-balancing mode upon reaching the top of the step and continues itsforward movement. If it reaches another step, the situation isequivalent to that depicted in step (1).

The second scenario is that the vehicle has not reached the top of thestairs, nor is the angle of the edges of successive steps fromhorizontal relatively shallow. In this case, the angle of the chassisfrom horizontal as the vehicle nears the top of the current step may beplanned to be nearly the same as the angle of the edges of successivesteps from horizontal. By planning the maneuver in this manner, theproximal end of the vehicle will reach the edge of the next step whilestill in contact with the edge of the previous step, as in step (8). Thecenter of mass may then be adjusted to be over the edge of the nextsteps (9) and (10), and the process described in steps (4) through (7)is repeated, as illustrated in steps (11) through (15).

Various combinations of the above steps can be used to maneuver therobot into positions for performing a desired task. The inventive robotis able to perform this and similar tasks because it operates, or can beoperated, to shift its center of gravity to balance on a small point bychanging the angle between the arms and the chassis, and by using thetreads or wheels to “catch itself” before it falls.

The multi-modal robot of the second embodiment is capable of performinga wide variety of maneuvers with the minimal set of actuators, thussaving cost and weight. Additional sensors can be mounted internally orexternally, such as contaminant sensors, Global Positioning System (GPS)receivers, wind sensors, analog or digital cameras, optical or radiationsensors, among many other possible uses. End effectors may be mounted onthe mobile robot platform 104 or arms 110, 120 or 119, such as linkagemechanisms with a gripper, solid or liquid collection systems, lightingsystems, or weapons systems, among many others.

An alternative configuration of the second multimodal robot embodimentis illustrated in FIGS. 16 a-c. In this configuration, shifting of thecenter of gravity is still used, however the manner in which theshifting is effected is different.

In this embodiment, the robot includes a chassis 148 and an actuatedboom 150. The chassis 148 is driven by a pair of treads 152, 154 (orconventional wheels 156 may be substituted, as shown in FIG. 18). Theboom 150 has significant mass. In the exemplary embodiment, the mass ofthe boom is approximately equal to the mass of the chassis. As in theprevious embodiment, motors are configured on the robot to drive thetreads (or wheels) and to change the angle of the boom 150 with respectto the chassis 148.

The hip joint described above with reference to FIG. 19 may also beincorporated in the configuration that uses a boom for shifting thecenter of gravity. In this case, the boom motor (which corresponds tothe balancing motor) will activate rotation of the boom arm.

The second multimodal robot embodiment includes sensors to detect therobot's configuration. Feedback control is applied to enable the vehicleto balance on its front or rear cogs (or wheels). The vehicle can alsoclimb obstacles (including stairs) by extending the mass of the boom 150over the obstacle and rotating the chassis up and over. This maneuvermay be done in a statically stable manner or in a dynamically balancedmanner. The boom arm may be extensible and/or may itself be configuredwith wheels or treads, in a manner similar to the wheels 126 in theprevious configuration.

As in the first multimodal robot embodiment, the configuration with theboom 150 takes advantage of the weight of the batteries for use as afunctional mass. An electrical connection is made between the boom andthe chassis to transmit the power from the batteries to the motorshoused within the chassis. In the exemplary embodiment, this connectionis made with slip rings, steel shafts riding in bronze bushings, as inthe hip joint describe above. The slip rings allow the boom to berotated about the chassis with no angular limitation.

In this configuration, the treads of the robot are in contact with thesurface at one point and the robot maintains its balance by adjustingthe boom to keep its center of gravity in line with the contact point.Inertial sensors (e.g. accelerometers and gyroscopes) may be used inconjunction with contact sensors (e.g. force sensitive resistors) insidethe tread assemblies to determine the contact point.

The second multimodal robot embodiment uses multiple commercialoff-the-shelf (COTS) sensors (MEMS-based accelerometers and gyroscopes,and optical encoders 134 (shown in FIG. 19) to estimate the angle of thechassis with respect to gravity (in the configuration of FIG. 14) andthe angle of the boom arm with respect to the chassis (in theconfiguration of FIG. 16). The programming of the robot includes acontrol system (which may include a Kalman filter) to actuate the motorsto dynamically balance the robot. The current prototype also acceptsmanual input via a COTS radio frequency remote.

In one application of the second multimodal robot embodiment, an “army”of the robots was deployed in an open, paved area (a parking lot) aroundwhich plumes of colored smoke were released. Each robot was equippedwith a sensor pack and electronics to measure smoke concentrations andwind velocities. The measurements were transmitted in real time (viaWiFi and 3G cellular data links) to an off-site supercomputer runningadvanced weather-forecasting type algorithms. These algorithms, in turn,synchronized a numerical simulation of the smoke plume with the actualmeasurements taken in the field in real time (a problem known as dataassimilation), then told the vehicles where to move next in order tominimize the uncertainty of the forecast. The goal of the system, whichwas successfully realized in the experiment, was to forecast where thesmoke was going to go, as precisely as possible, before it got there,while coordinating the vehicles in real time to collect the mostvaluable information possible for the particular wind conditions presentduring that test. The research has important social relevance related tonew technology and algorithms for tracking a wide variety ofenvironmental plumes of interest, from gulf-coast oil, to Icelandicvolcanic ash, to possible chemical/radioactive/biological plumes inhomeland security settings.

Third Multimodal Robot Embodiment

In a third embodiment, a spherical robot incorporates momentum exchangedevices to achieve rapid acceleration or deceleration in any direction.

As illustrated in FIG. 23, an exemplary embodiment of the sphericalrobot according to the present invention includes a frame 202 forsupporting a plurality of momentum-exchange elements 204 so that theelements are distributed relative to the surface of a spherical shell210 that encloses the frame 202, elements 204, and all controlelectronics, actuators and batteries that are required to power andcontrol the robot. Sensors may also be included to provide feedback tooptimize balancing and locomotion under different conditions. Thecontrol electronics may include wireless communication devices forcommunication with a remote computer, mobile phone or other wirelessdevice. Alternatively, the spherical robot may be tethered to acontroller, such as a joystick, track ball or the similar externalcontrol device.

The basic elements of three different momentum exchange elements thatmay be used in the spherical robot are shown in FIGS. 24 a-24 c. Thereaction wheel assembly (RWA) shown in FIG. 24 a includes a single motorfor spinning the wheel. A single gimbal control moment gyro (SGCMG) isshown in FIG. 24 b. This assembly includes two motors, one for spinningthe wheel, the other for rotation of the gimbal, allowing the directionof the wheel angular momentum to be varied. In FIG. 24 c, a doublegimbal control moment gyro (DGCMG) is shown, with three motors,including the two used in the SGCMG plus a third motor to vary the planeon which the SCGMG sits.

In the configuration of the fourth embodiment that is shown in FIGS. 23and 26, a cubical frame 202 is populated with four single-gimbal CMGs204 a-204 d, with each gimbal axis 206 a-206 d at an angle extendingacross each of four faces 208 a-208 d. This makes the inventive robotparticularly agile, as the momentum needed to maneuver is stored withinthe SGCMGs and, thus, does not need to be generated by high-torque,large electrical power-consuming motors as in standard direct drivesystems of the prior art. The SGCMGs may be operated individually orsimultaneously to effect the desired function, such as rolling,steering, stationary rotation around the contact point or balancing inposition. While frame 202 is shown in a cubical configuration, it may beconstructed with virtually any geometric shape that fits within aspherical shell, including pyramidal, conical, symmetric, skewed, lineararrangements combined with 3-D structures, and various othercombinations of such shapes. FIG. 25 illustrates a few of a largevariety of possible arrangements of momentum exchange elements,including a pyramid, skewed cone, symmetrical octahedron, and roof-typewith linear combinations of elements. Virtually any geometrical shapecan be used that will allow momentum to be generated in a plurality ofdifferent directions for steering, rolling, balancing, etc. Further, therobot is not limited to spheres as an outer structure, but may includegeneralized amorphous ellipsoidal configurations as well.

The shell 210 that is used to enclose the frame, momentum exchangeelements, the actuators and control electronics may be formed from awide range of materials, selection of which will depend on the intendedapplication and will be within the level of skill in the art. Ingeneral, the outer surface of the shell should be capable of generatingsufficient friction with the surface on which the robot will be movingto efficiently convert the action of the momentum exchange elements intomotion in the desired direction. The material may be a rigid, preferablyimpact-resistant plastic or polymer, which may include carbon-fiber orfiberglass, among others. In some applications in harsh environments,metals, metal-composites, or specialized materials such as KEVLAR®composites, may be appropriate for particularly hazardous applications.In other applications, it may be appropriate to use a layered structurethat includes padding for shock absorption, thermal insulation or otherprotective covering, such as NOMEX® or other fire-retardant materialthat can be incorporated in or underneath a hard exterior shell.

FIG. 26 provides a three-dimensional drawing of an exemplaryimplementation of the inventive spherical robot. As illustrated, theframe 202 should fit snuggly within the spherical shell 210. For theexample of a cubic frame, the corners of the frame may be chamfered, asshown, to provide a broader, angled and somewhat rounded surface tocontact the inner surface of the shell (as opposed to having sharpcorners on the frame). This provides uniform structural support for theshell 210 while ensuring that the frame 202 and the components mountedthereon are stably supported, i.e., so that the frame does not moverelative to the shell.

As illustrated, each SGCMG 204 a-d incorporates the spin motor (theshaft of the spin motor 220 can be seen in FIG. 26) and reaction wheelwithin a small, flat cylindrical housing, which is fixedly mounted onthe corresponding gimbal axis 206 a-206 d. Power for driving the spinmotor is provided through wires running through the corresponding gimbalaxis. One end of each gimbal axis is attached the shaft of a gimbalmotor 222, while the other end of the axis is supported within a pivotso that the axis and reaction wheel rotate when driven by theircorresponding gimbal motor.

All electronic components for operating, communicating with, andcollecting data, if appropriate, including all wiring and connectors,will be housed within shell 210, preferably centered within frame 210 toplace the weight at the center of the sphere. The components, which mayinclude one or more printed circuit boards with associated batterycasings or other holders, may be supported on a bar or plate thatextends between opposite corners of the cube or between the upper face208 e and lower face 208 f of the cube as illustrated, so as not tointerfere with movement of the elements 204. Some of the components,e.g., the batteries, may alternatively be mounted within the insideedges of the frame if the frame is hollow. In an alternative embodiment,elements 204 may be mounted on all 6 faces of the cube, or on all facesof a selected geometric structure, as long as sufficient space isprovided to avoid interference between movement of momentum exchangeelements and other components of the system.

FIGS. 27 a and 27 b illustrate an alternative construction of thespherical robot with the outer shell removed. In this case, the frame232 is formed by the intersection of four open-centered disks 234 a-dthat correspond to faces 208 a-d of FIGS. 23 and 26. The rounded facesprovide additional structural support for the spherical shell. The tophousing 236, which encloses the control electronics is attached to thetop of frame 232.

Referring to FIG. 27 b, which shows an exploded view of the fullassembly with one SGCMG also in exploded view, the frame is defined bythe assembly of faces 234 a-234 d with top plate 244 and bottom plate245, which are attached by brackets 242. In addition to the top housing236, attached to the upper surface of top plate 244 are a number ofbattery holders 240 for retaining batteries 238. As illustrated, thebatteries are button style lithium batteries. Additional battery holders240 and batteries 238 are located on the outer surface of bottom plate245 along with the gimbal motor controllers 246.

FIG. 27 c shows an exploded view of SGCMG 250 shown in FIG. 27 b. Therotor 268 is attached to the rotor shaft 270. The rotor provides theinertia for the momentum storage of a SGCMG. The rotor and rotor shaft268, 270 are held in place relative to the outer housing formed from thecombination of 256, 259, 260, 267, 272 and 278, by a journal 252, 277and thrust bearing 258, 271 combination. The shaft of the spin motor 254is attached to the rotor shaft 270 and the spin motor 254 is attached tothe c-ring 252, which is also attached to the bottom plate 256 of thehousing. The spin motor 254 rotates the rotor 268 at a constant rate (inthe SGCMG case) or varies the angular rate (in the VSSGCMG case) viafeedback from the optical encoder 280 and spin motor electronics 282.The rotor speed is measured by the optical encoder 280, which isattached to the top plate 276 of the housing. The spin controlelectronics 282 are mounted to mounting posts 279, which are alsoattached to the top plate 276 of the housing. The housing assembly 256,259, 260, 267, 276, 278 is attached to gimbal shafts 269, 273. Onegimbal shaft 269 is attached to a spur gear 262, which is free to rotaterelative to the right gimbal mounting bracket 264 via a thrust/journalbearing combination. This spur gear 262 is kinematically constrained toa second spur gear 263 which is attached to the gimbal motor 261 and isalso free to rotate relative to the right gimbal mounting bracket. Thesecond gimbal shaft 273 is rigidly attached to the slip ring assembly274 and is free to rotate relative to the left gimbal mounting bracket276 via a thrust/journal bearing combination. The slip ring assembly 274provides power (in spite of the continuous rotation of the gimbal) tothe spin motor controller 282. The angular rotation of the gimbal shaft273 is measured by a potentiometer 275 whose movable part is attached tothe gimbal shaft and immovable part is attached to the left gimbalmounting bracket (28). The left 276 and right 264 gimbal mountingbrackets are attached to the sidewall 234 a.

In one embodiment, the spherical robot may have pressure bladdersattached on the inner surface of the shell 210 or on non-interferinglocations on the frame 202. (A single exemplary pressure bladder 214 isdiagrammatically illustrated in FIG. 23). The bladders will preferablybe uniformly distributed around the inner surface of the shell, e.g., onthe edges of two opposite faces of the cube, to control buoyancy,thereby allowing the robot to float on the surface of a liquid, e.g., anatural or artificial body of water, or to move fully- or partiallysubmerged below the surface. Operation of the momentum exchange elementswill allow the buoyant robot to move within or over the surface of thebody of water as the robot spins, thus providing an amphibious vehicle.In one implementation, the bladders may be pre-filled to the desiredbuoyancy prior to deployment of the robot via a valve accessible throughthe shell. In another approach, small compressed gas canisters, as areknown in the art for use in life vests and buoyancy compensators, may bemounted on the frame in communication with a feedback system that willdetermine the conditions in the body of water, e.g., temperature,surface turbulence and weather conditions, and control the amount of gasreleased into the bladders to achieve the desired buoyancy and frictionwith the water's surface to maneuver effectively and efficiently. Bleedvalves on the bladders may also be provided to actively adjust thebuoyancy as needed under changing conditions. The gas canisters may bereplaced with new canisters after one or more uses.

Alternatively, the robot can be made passively buoyant through materialselection. For example, the frame can be constructed using a lightweightmaterial such as plastic, wood or fiberglass, or using lightweightmetals such titanium or aluminum when the strength and durability ofmetal is required. The material used for the frame can also be hollow orpartially-hollow, e.g., honeycomb structures or extruded channel. Theshell, which would need to be a continuous surface without any openingsto make it watertight, could be a formed from a buoyant plastic orpolymer, such as polystyrene, neoprene or closed cell foam. The buoyantfoam structure could be covered with an impervious outer skin orcoating, such as a lightweight metal, for applications where metal ispreferred, or an epoxy resin or other polymer, using a constructionsimilar to that used in typical surfboards. Openings (ports or doors) inthe shell for accessing the interior components of the robot would needto be sealable to produce a watertight closure.

FIG. 28 provides a block diagram of an exemplary control architecturethat can be used with the spherical robot. As will be recognized bythose in the art, other control architectures can be use. The pathgeneration block can be achieved by the relationship between thevelocity of the body and the angular rate. The ACS control law block,pseudoinverse CMG steering law block, and gimbal angular rate controllerblock can be derived using procedures and algorithms that are known inthe art.

Locomotion within a body of liquid can be achieved by activating themomentum exchange elements to rotate the robot's body in the directionof desired motion, the same as would be used on land. FIGS. 29 a-cillustrate different applications of the spherical robot. Using a seriesof cartoons depicting an exemplary robot with a single RWA, FIGS. 29 aand 29 b illustrate a free-surface case and a near-a-surface case,respectively. In FIG. 29 a, in a fluid, when the RWA spins one direction(counter-clockwise as shown), the sphere spins in the opposite direction(clockwise as shown). The fluid's interaction between the rotatingsphere and the free-surface causes the sphere to move in translation tothe left, as dictated by known analytical solutions to the Navier-Stokesequations, which prove that a rotating sphere in an incompressibleviscous fluid near a wall (or free surface) can move in a translationaldirection orthogonal to the angular rate and parallel to the wall (orfree surface). See. e.g., J. Happel and H. Brenner, Low Reynolds NumberHydrodynamics: with special applications to particulate media, Springer1983, which is incorporated herein by reference. In FIG. 29 b, whichrepresents movement on top of a surface, when the RWA spins onedirection (clockwise as shown), the sphere spins in the oppositedirection (counter-clockwise as shown), propelling the sphere to theleft.

A plurality of spherical robots can work in cooperation to facilitatelocomotion and overcoming various obstacles. As illustrated in FIG. 29c, a sequence of steps is shown for stacking a number of sphericalrobots to increase the height of one or more robots, thus giving theuppermost robot(s) an increased perspective to for collection of visualinformation or for other tasks that may require an obstacle to beovercome. In step 1, three spherical robots, designated as A, B and C,start off positioned side-by-side on a support surface. Robots A and Cmove toward robot B to squeeze B upward in step 2. In step 3, A and Ccome together with B balanced on top. In step 4, robots D and E areadded to the mix, with C and E being moved toward each other to squeezeD upward. A will move along with C to keep B on top. In step 5, B and Dare on top after C and E come together. Added spherical robots F and Gcombine with E in step 6 to force F upward, after which B, D and F aresupported on top of A, C, E and G. In step 7, B and F move toward eachother to squeeze D upward. In step 8, D moves up and to the right toclimb up on F while B moves back to the left. In step 9, the dynamicbalancing ability provided by the multiple momentum exchange elements ofeach robot allows D to balance on top of F which in turn balances on topof E, as shown in step 9. Stacking the spherical robots makes itpossible to position a robot with a camera or other sensor to look overan obstacle. Thus, the spherical robot, while taking advantage of a lowprofile to approach a target by passing under a variety of obstacles, astill able to cooperate with other similar robots to enable climbing toovercome obstacles.

In an exemplary application, multiple spherical robots can be deployed,with each robot carrying a different instrument or payload. The deployedrobots can cooperate to enable the robot carrying a particularinstrument to position itself optimally for completing its task. Inmilitary or law enforcement applications, the above-described sphericalrobot can be used in covert reconnaissance or munitions delivery.Commercial applications of the robot include incorporate of the robot atoy or a therapeutic device.

Fourth Multimodal Robot Embodiment

FIGS. 30-36 illustrate a fourth embodiment of the multimodal robot,which is a wirelessly-controlled vehicle that can perform the tasks ofobject retrieval, storage and throwing. The design includes anintegrated ball pick up mechanism and a throwing arm. Although describedin the example as a ball-handling robot, the fourth embodiment is notlimited to balls, but may be adapted to pick up and throw other objectsthat are sufficiently symmetric to allow the pick-up mechanism to work.Similarly, the throwing arm, described in the example as “jaialai-style”, is not limited to a jai alai shape, but may be of differentshapes depending on the desired speed, trajectory and spin of the objectbeing thrown.

To enable ball pick up, the body and wheels of the robot are spaced toprovide automatic pickup and loading of the target balls. This featureallows the operator to drive the robot toward the target, with thecurvature of the robot directing the ball into the space between thewheel and the body. The rotation of the wheel brings the ball up to bestored within a basket or other storage receptacle.

For throwing, the robot is stabilized by a feedback control circuit tobalance upright as an inverted pendulum. The rotational inertia producedby the motors that drive the wheels allows the robot to rotate the bodyrapidly from a lay-down mode to an upright mode. This rapid rotationresults in the effective toss of a lightweight ball. The exemplary shapeof the throwing arm imparts a spin to the ball as it rolls off thethrowing arm track, resulting in a more stable and longer throw.

As illustrated in FIGS. 30 and 31, the fourth robot embodiment 300includes a molded body 302 that is roughly cylindrical in shape(circular as viewed from the side) with a diameter and a width (betweenthe wheels) that is approximately three times the diameter of the targetobject. In the exemplary embodiment, the target object is a ping pongball with a diameter of about 40 mm. Two coaxial wheels 306 are mountedon a rotational axis 303. Each wheel 306 is independently driven by amotor (not shown) that is responsive to active feedback controls toprovide the robot with a self-balancing function. Control electronicsfor receiving feedback and actuating the motors are mounted on a printedcircuit board (not shown) that is housed under a removable back cover309. One or more batteries (not shown) for providing power to the motorsand electronics are preferably enclosed within the lower portion of body302, below the rotational axis 303, and are also accessible through backcover 303. The center of gravity of the robot is above the rotationalaxis so that when the motors are disconnected from its power source,i.e., switched off, the robot falls over.

The vertical arm 304 is configured as a track for launching the objectas well as being a mass the enables backward and forward motions throughleaning. In the exemplary embodiment, the track has a slight curvaturethat is similar in design to a jai alai cesta (basket). When the robotleans forward, it moves forward to restore vertical balancing. Turningis facilitated by rotating the wheels in opposite directions.

The feedback controls that enable self-balancing rely on a comparison ofthe signals of two MEMS (micro electro-mechanical systems)accelerometers, which are well known in the art. One such accelerometer324 is located on a platform 322 near the upper end 318 of the verticalarm 304. The feedback from this sensor may be turned off or ignored toallow a horizontal orientation of the robot with the arm 304 (actually,the bottom surface of platform 322) dragging on the support surface, asshown in FIG. 36 a. Orientation in the horizontal mode is necessary toinitiate the throwing process. The second accelerometer is locatedcoplanar with, and at a fixed distance from, the first. In the exemplaryembodiment, the second accelerometer is located on the printed circuitboard under removable back cover 309, near the axis of rotation 303 ofthe wheels 306. Comparing the signals from the two accelerometers yieldsdecoupled rotational and translational acceleration measurements.

Referring to FIGS. 31 a and b, the pick-up mechanism comprises acircular channel 312 formed on each side of a central plane bisectingthe robot between the lower portion of body 302 and the inner surface ofthe wheel 306. The body has a peaked leading edge 310 that is coincidentwith the central plane. The leading edge 310 acts as a guide, similar tothe bow of a ship, to direct the target object (ball) to one side of thecenterline and toward one of the channels 312. The scooped contour ofthe hub sections 308, in combination with the inner surface of thewheels and the guide 310, define channels 312, which direct the ballinto position for pick-up. The inner surface of each wheel has acompressible foam insert 307 to generate friction against the ball,causing it to be captured within the channel to be drawn along with thewheel as it rotates. Other methods for generating sufficient friction tocapture the ball between the hub and the inner surface of the wheel maybe used, including spring-loaded tracks, other compressible/resilientsurfaces, or rough textures molded into or applied to the inner surfacesof the wheels to generate sufficient friction to pull the ball into thechannel.

Referring to FIGS. 32 a and 32 b, as the wheel 306 rotates forwardrelative to the body, the ball rolls within the channel 312 into astorage volume 316 located at the center of a hollow portion of body302, between hubs 308. (For clarity, the body is shown with the wheelremoved.) Since the robot is able to turn on a point due to theindependent operation of the wheels, similar to a treaded vehicle, ballpickup is possible even when the robot spins in place, as long as thewheel in contact with the ball is moving forward with respect to thebody 302 to draw the ball into the channel.

Referring again to FIGS. 31 a and 31 b, in the upper portion of body302, channels 312 continue into a curved passageway defined by channelcovers 314, which help guide the ball into the storage volume 316 withinthe body 302. At the opening defined by the edge of each channel cover314 is a spring loaded flipper 330. A detailed view of the flipper 330can be seen in FIG. 33. The flipper 330 is depressed by the ball as itenters the channel cover 314 and approaches the storage volume, thenresiles once the ball is past to extend up into the channel 312 toprevent the ball from leaving the storage volume through the channel.Once the ball is in the storage volume 316, it is ready to be thrown.

The ball release mechanism 340, illustrated in FIGS. 34 a and 34 b, ismounted within the center of body 302 within the storage volume 316.(The location of mechanism 340 can be seen in FIGS. 35 a-35 c.) The ballrelease mechanism consists of a gate 342 which is connected to a servomotor 344 by a push rod 346 and a cylindrical sliding collar 347. Thepush rod 346 slides freely along the axis of the cylindrical slidingcollar 347 and is displaced in the direction normal to the cylindricalsliding collar. The servo motor 344 may be radio-controlled or activatedby a system controller (not shown). The gate 342 has a curved surfacethat is shaped to match the exterior dimensions or the ball. The arclength and/or angle of the gate is preferably large enough to preventpassage of multiple balls while being small enough to minimize servomovement and release time.

FIGS. 35 a-35 c are cross-sectional views of the robot body illustratinga sequence of steps within the ball release function. In FIG. 35 a, therobot 300 is in an upright orientation, which is the appropriateorientation for collecting the balls for storage within the storagevolume 316. The ball release mechanism 340 is in its normally closedposition to prevent balls from escaping from the storage volumeunintentionally. The shape of the gate 342 allows a single ball to sitat the base 348 of the throwing arm 304 while the robot is upright. Thebottom of storage volume 316 is sloped toward the rear of the body toencourage the ball toward the throwing arm base 348.

FIG. 35 b shows the robot after rotation of the body and throwing arm toa horizontal orientation. The gate 342 of ball release mechanism 340remains closed to prevent balls 320 from rolling out of the storagevolume.

In FIG. 35 c, when the throwing function is to be executed, the servomotor 344 of ball release mechanism 340 is triggered to open the gatebriefly to allow one ball 320 onto the track of throwing arm 304.

FIGS. 36 a-36 d illustrate a sequence of steps of the throwing orlaunching function. By conservation of angular momentum around therobot's center of gravity, the throw can be performed by rapid reverseacceleration of the wheels 306 in a direction away from the throwingarm. This causes the body 302 to suddenly rotate in the oppositedirection, so that the throwing arm 304 quickly rotates up and forward.As seen in FIGS. 36 b-36 d, the throwing motion imparts a forwardvelocity on the ball relative to the support surface. Because the ballrolls along the track rather than sliding up to the release end 318, thetrack imparts a backspin on the ball 320, which improves flightstability and effective range.

The fourth embodiment of the multimodal robot may be controlled remotelyby wireless communication with a simple joystick and/or push buttoncontroller, or it may possess sensors (optical, audio, temperature,chemical, etc.) and internal circuitry including a computer controllercapable of effecting autonomous behavior with adaptive response to thesensor feedback of environmental conditions. Using vision, motion, heator other object detection technology, the robot may be capable oftracking and seeking a target object to pick up, store and throw to auser or another robot. Another potential embodiment may consist of justobject pick up and storage for the purpose of object retrieval andtransport. Adaptive behavior would, for example, allow the robot to beoperated in horizontal mode to pass under obstacles or to maintain a lowprofile to avoid detection, shifting to the vertical orientation asneeded to pick up an object and return to horizontal mode to initiate alaunching sequence. Additionally, the robot may be configured forcatching as well by means of a modified track. The appeal of a catchingrobot is the active responsiveness of the robot's self-balancing. Thecombined abilities of the fourth multimodal robot embodiment to catch,throw, seek and pick up objects autonomously would allow for “team”sports or robotics competitions.

The above-described multimodal robots all incorporate a number of designfeatures that are important to their successful operation. Thesefeatures include (1) multifunctional wheels, which are used formain-drive, differential-steering wheels, upright actuators, reactionwheels, counterweights and ball pick-up mechanisms; (2) multifunctionalmotors used to produce completely different effects when drivenclockwise or counterclockwise by virtue or creative use of latchingmechanisms; (3) sensors that provide feedback to a system controller forreactive actuation of motors for balancing and locomotion; and (4)custom printed circuit boards used to connect exactly the rightelectronics together with a minimum footprint and mass, in addition tohigh-performance COTS boards such as the Texas Instruments C2000 MCU(used in the first embodiment), the National Instruments sbRIO 9602(used in the second embodiment) and the Technologic Systems TS-7250(used in the third embodiment), with both low-level coding in C as wellas high-level control design leveraging MathWork's MATLAB® SIMULINK®software and National Instrument's LabVIEW™ CD&Sim™ modules,respectively, to program the Texas Instruments and National Instrumentsboards.

The above-described robots by may be combined to perform a variety ofdifferent tasks that may be useful in areas including defense,counterterrorism, surveillance and law enforcement, industrialapplications, such as transport of payloads and environmental monitoringin areas that are hazardous or otherwise difficult to access, spaceexploration, entertainment, along with many other possible uses. Forexample, features of the tracked robot of the second embodiment could becombined with the throwing function of the fourth embodiment to allow arobot to travel over rough terrain and/or climb over obstacles, thedeliver an object by launching it using the throwing functions of thefourth embodiment.

While the foregoing written description contains many specifics, theseshould not be construed as limitations on the scope of the invention orof what may be claimed, but rather as descriptions of features specificto particular embodiments of the invention. Certain features that aredescribed in this specification in the context of separate embodimentscan also be implemented in combination in a single embodiment.Conversely, various features that are described in the context of asingle embodiment can also be implemented in multiple embodimentsseparately or in any suitable sub-combination. Moreover, althoughfeatures may be described above as acting in certain combinations andeven initially claimed as such, one or more features from a claimedcombination can in some cases be excised from the combination, and theclaimed combination may be directed to a sub-combination or variation ofa sub-combination.

The invention claimed is:
 1. A robotic system comprising: a body havinga body front, a body back, body sides with a body width therebetween,and a lower body portion having a peaked center and a lower body widthless than the body width, the body having a cavity therein defining astorage volume configured for retaining at least one object, each bodyside defining a hub having an axle defining a rotational axis, whereinthe body has a center of gravity disposed above the rotational axis,wherein the peaked center is centered on the body front along a planebisecting the body and is configured to guide the at least one object toone side of the lower body portion; at least two wheels, wherein onewheel is rotatably mounted on each axle; at least two motors, whereinone motor of the at least two motors is configured for independentlydriving the wheel mounted on each axle; a system controller configuredto generate control signals adapted configured to actuate each motor;one or more sensors configured to generate feedback signals to thesystem controller, in response to which the system controller reactivelyactuates the at least two motors so that the body self-balances andfurther performs one or more functions selected from the groupconsisting of forward motion, backward motion, lying down, retrieving anobject, carrying an object, throwing an object and catching an object;an object retrieval mechanism configured for picking up at least oneobject and placing the at least one object in the storage volume, theobject retrieval mechanism comprising a channel disposed on each side ofthe peaked center, the channel having an exit end in communication withthe storage volume and an entrance end defined by the hub, the lowerbody portion and an inner surface of the wheel, wherein the channel hasa dimension configured for receiving the at least one object whereby africtional contact is created between the inner surface of the wheel andthe channel, wherein rotation of the wheel draws the object into thechannel and into the storage volume; and a power source for configuredfor powering the motors, the system controller and the one or moresensors.
 2. The robotic system of claim 1, further comprising: anelongated arm extending away from the body perpendicular to therotational axis, the elongated arm having a base portion incommunication with the storage volume.
 3. The robotic system of claim 2,wherein at least one motor drives a corresponding wheel in a forwarddirection to draw the object into the channel.
 4. The robotic system ofclaim 2, wherein the motors are configured for rotating the bodyrelative to the wheels so that the elongated arm is oriented in ahorizontal position.
 5. The robotic system of claim 2, furthercomprising a release gate disposed between the storage volume and thebase portion of the elongated arm, wherein activation of the releasegate releases an object to pass from one of the storage volume and thebase portion to the other.
 6. The robotic system of claim 5, whereinwhen the elongated arm is oriented in a horizontal position, activationof the release gate releases the object to the base portion.
 7. Therobotic system of claim 2, wherein the elongated arm comprises a curvedtrack upon which the object rolls.
 8. The robotic system of claim 2,wherein the one or more sensors comprise at least two accelerometers formeasuring rotational and translational acceleration, and wherein thesystem controller is configured for comparing measured acceleration forcontrolling the motors for self-balancing.
 9. The robotic system ofclaim 2, wherein the system controller is responsive to a wirelessremote control signal.
 10. The robotic system of claim 2, wherein theone or more sensors comprise sensors for detecting location of an objector another robot.
 11. The robotic system of claim 10, wherein the systemcontroller responds autonomously to feedback from the sensors.
 12. Arobotic system comprising: a body comprising a cylinder having arotational axis, the cylinder having two ends, each end defining a hubhaving an axle aligned with the rotational axis, the body having acavity therein defining a storage volume configured for retaining anobject; a wheel rotatably disposed on each axle; a motor configured forindependently driving each wheel; an elongated arm extending away fromthe body perpendicular to the rotational axis, the elongated arm havinga base portion in communication with the storage volume; a lower bodyportion disposed on the body opposite the elongated arm, wherein thelower body portion is symmetrical along a plane bisecting the cylinder;and a curved channel disposed on each side of the bisecting plane havingan exit end in communication with the storage volume and an entrance enddefined by the hub, the lower body portion and an inner surface of thewheel and having a dimension configured for receiving the object toproduce a frictional contact between the inner surface of the wheel, thehub and the lower body portion, wherein rotation of the wheel draws theobject into the channel and into the storage volume; a system controllerconfigured for generating a signal for actuating each motor; one or moresensors in communication with the system controller configured forgenerating feedback signals for reactively actuating the motors toperform one or more functions selected from the group consisting offorward motion, backward motion, lying in a horizontal orientation,self-balancing, retrieving the object, carrying the object, throwing theobject and catching the object; and a power source for providing powerto operate the motors, the system controller and the one or moresensors.
 13. The robotic system of claim 12, wherein at least one motordrives a corresponding wheel in a forward direction to draw the objectinto the channel.
 14. The robotic system of claim 12, wherein the motorsare configured for rotating the body relative to the wheels so that theelongated arm is oriented in a horizontal position.
 15. The roboticsystem of claim 12, further comprising a release gate disposed betweenthe storage volume and the base portion of the elongated arm, whereinactivation of the release gate releases an object to pass from one ofthe storage volume and the base portion to the other.
 16. The roboticsystem of claim 12, wherein when the elongated arm is oriented in ahorizontal position, activation of the release gate releases the objectto the base portion.
 17. The robotic system of claim 12, wherein theelongated arm comprises a curved track upon which the object rolls. 18.The robotic system of claim 12, wherein, when the elongated arm is in ahorizontal position, rapid activation of the motors rotates thecorresponding wheels in a first direction causing the body to rotatearound the rotational axis in an opposite direction to rapidlyaccelerate the horizontal arm toward a vertical position.
 19. Therobotic system of claim 18, wherein the object disposed on the baseportion of the elongated arm rolls toward a distal end of the arm as theelongated arm accelerates toward the vertical position, wherein theobject is thrown when the object reaches the distal end of the arm. 20.The robotic system of claim 12, wherein the one or more sensors compriseat least two accelerometers configured for measuring rotational andtranslational acceleration, and wherein the system controller isconfigured to compare measured acceleration for controlling the motorsfor self-balancing.
 21. The robotic system of claim 12, wherein thesystem controller is configured to respond to a wireless remote controlsignal.
 22. The robotic system of claim 12, wherein the one or moresensors comprise sensors configured for detecting location of theobject, an obstacle, or another robot.
 23. The robotic system of claim22, wherein the system controller responds autonomously to feedback fromthe sensors.
 24. The robotic system of claim 1, further comprising anobject release mechanism, comprising: a release opening disposed in thebody, wherein the release opening is configured to permit the at leastone object to pass therethrough; and a gate mechanism configured toprevent the at least one object from exiting through the releaseopening; wherein the at least two motors further comprise a gate motorconfigured for activating the gate mechanism to release the object inresponse to control signals from the system controller.
 25. The roboticsystem of claim 24, further comprising an object throwing mechanismconfigured to, in response to a control signal, impart a forwardvelocity to the at least one object when the gate mechanism releases theobject.
 26. The robotic system of claim 25, wherein the object throwingmechanism comprises an elongated arm extending away from the bodyperpendicular to the rotational axis, the elongated arm having a baseportion in communication with the release opening, wherein, when thebody is oriented in a horizontal position, activating the gate mechanismreleases the object to the base portion.
 27. The robotic system of claim26, wherein, when the elongated arm is in a horizontal position, rapidactivation of the motors rotates the corresponding wheels in a firstdirection causing the body to rotate around the rotational axis in anopposite direction to rapidly accelerate the horizontal arm toward avertical position to launch the object.
 28. The robotic system of claim1, wherein the one or more sensors comprise at least two accelerometersconfigured for measuring rotational and translational acceleration, andwherein the system controller is configured to compare measuredacceleration for controlling the motors for self-balancing.
 29. Therobotic system of claim 1, wherein the system controller is responsiveto a wireless remote control signal.
 30. The robotic system of claim 1,wherein the one or more sensors comprise sensors for detecting locationof an object or another robot.
 31. The robotic system of claim 1,wherein the one or more sensors are selected from the group consistingof accelerometers, optical sensors, audio sensors, temperature sensors,motion sensors, and chemical sensors.
 32. The robotic system of claim31, wherein the system controller responds autonomously to feedback fromthe sensors.
 33. The robotic system of claim 1, wherein the body furthercomprises a platform configured for carrying a payload.
 34. The roboticsystem of claim 12, wherein the one or more sensors are selected fromthe group consisting of accelerometers, optical sensors, audio sensors,temperature sensors, motion sensors, and chemical sensors.
 35. Therobotic system of claim 34, wherein the system controller respondsautonomously to feedback from the sensors.
 36. A robotic systemcomprising: a body having a body front, a body back and body sides witha cavity therein defining a storage volume configured for retaining atleast one object, the body having a rotational axis and a center ofgravity above the rotational axis, each body side defining a hub havingan axle aligned with the rotational axis, wherein the body furthercomprises a lower body portion having a peaked leading edge centeredbetween the body sides configured to guide an object to one side of thelower body portion; a pair of wheels, wherein one wheel is rotatablydisposed on each axle; at least two motors, wherein one motor isconfigured for independently driving each wheel; an object releasemechanism comprising a release opening in communication with the storagevolume, wherein the release opening is configured to pass the objectfrom the storage volume and outside of the body; a channel disposed oneither side of the lower body portion, the channel having an exit end incommunication with the storage volume and an entrance end defined by thehub, the lower body portion and an inner surface of the wheel and havinga dimension configured for receiving the object and producing africtional contact between a surface of the object and the inner surfaceof the wheel and the channel, wherein rotation of the wheel draws theobject into the channel and into the storage volume; one or more sensorsconfigured for generating feedback signals indicative of an orientationof the body; a system controller configured for generating actuationsignals to each motor in response to the feedback signals to reactivelyactuate the motors to control rotation of the wheels so that the bodyself-balances and further performs one or more functions selected fromthe group consisting of forward motion, backward motion, lying in ahorizontal orientation, retrieving an object, carrying an object,throwing an object and catching an object; and a power source configuredfor powering the motors, the system controller and the one or moresensors.
 37. The robotic system of claim 36, wherein the object releasemechanism further comprises: a gate configured to prevent the objectfrom passing through the release opening; a gate motor configured foractivating the gate for releasing the object in response to controlsignals from the system controller.
 38. The robotic system of claim 36,wherein the object release mechanism is further configured to activateone or more of the at least two motors in response to a control signalfor imparting a forward velocity to the object.
 39. The robotic systemof claim 36, wherein the one or more sensors comprise at least twoaccelerometers for measuring rotational and translational acceleration,and wherein the system controller compares measured acceleration forcontrolling the motors for self-balancing.
 40. The robotic system ofclaim 36, wherein the system controller is responsive to a wirelessremote control signal.
 41. The robotic system of claim 36, wherein theone or more sensors comprise sensors for detecting location of an objector another robot.
 42. The robotic system of claim 36, wherein the one ormore sensors are selected from the group consisting of accelerometers,optical sensors, audio sensors, temperature sensors, motion sensors, andchemical sensors.
 43. The robotic system of claim 42, wherein the systemcontroller responds autonomously to feedback from the sensors.
 44. Therobotic system of claim 36, wherein the body further comprises aplatform configured for carrying a payload.
 45. The robotic system ofclaim 2, wherein, when the elongated arm is in a horizontal position,rapid activation of the motors rotates the corresponding wheels in afirst direction causing the body to rotate around the rotational axis inan opposite direction to rapidly accelerate the horizontal arm toward avertical position.
 46. The robotic system of claim 45, wherein an objectdisposed on the base portion of the elongated arm rolls toward a distalend of the arm as the elongated arm accelerates toward the verticalposition, wherein the object is thrown when the object reaches thedistal end of the arm.